john writes
Does anyone use an Oyster Card for the tube? Is there an advantage over
just buying the tube pass?

There's no financial advantage. You benefit from the better security
and you get speedier passage through station gates.

I'm thinking of buying some kind of annual pass as it looks much
cheaper, but I'm just worried if I end up moving or something that I
may be caught out. Does anyone here buy the annual? Any regrets?

There's no difference between Oyster Travlecard and a conventional
Travelcard in that respect. There are special rules dealing with
situations where you need to change your zonal validity.

--
Dave